I think they've simply continued going up market and care less about smaller players.
If you are looking for transactional emails with a tightly integrated template builder, check out Waypoint. We're an alternative and have some different approaches: https://www.usewaypoint.com/compare/sendgrid-email-api-alter...
I was using SendGrid's WYSIWYG templates for many emails, but I'm re-doing them in my own code so that I can more easily change providers in the future. I'll just need the ability to send HTML emails.
I'm trying out MailTrap.